Immunoreactivity for the calcium binding protein, calretenin (calretinin- ir), was demonstrated in cell bodies of vagal and glossophyrngeal sensory ganglia (jugular, petrosal, and nodose ganglia) and in associated nerve fibers. In the jugular and petrosal ganglia, many calretinin-ir neurons were also immunoreactive for calcitonin gene-related peptide and substance P. In the nodose ganglion, most of the calretinin-ir neurons lacked these peptides. While the function of calretinin is unclear, its distribution suggests a role in the vagal and glossopharyngeal sensory systems. From the jugular ganglion, CGRP-and SP-ir neurons project to cerebral blood vessels, thyroid gland, trachea, carotid sinus and carotid body. From the petrosal ganglion, CGRP and SP neurons project to the carotid sinus, carotid body and taste buds. The coexistence of calretinin and these peptides in some jugular and in many petrosal neurons suggests that this calcium binding protein is associated with sensory transmission from the carotid sinus, carotid body and taste buds. Furthermore, we have shown that calretinin is observed in nerve fibers in the taste buds of the tongue and in the carotid body.